AU-C Section 220.10: Leadership Responsibilities for Quality on Audits

AU-C Section 220.10 says:

"The engagement partner should take responsibility for the overall quality on each audit engagement to which that partner is assigned. In fulfilling this responsibility, the engagement partner may delegate the performance of certain procedures to, and use the work of, other members of the engagement team and may rely upon the firm's system of quality control."

First, let's define a few terms noted in this requirement:

•  The engagement partner is the partner or other person in the firm who is responsible for the audit engagement and its performance and for the auditor's report that is issued on behalf of the firm and who, when required, has the appropriate authority from a professional, legal, or regulatory body.
• A partner is any individual with authority to bind the firm with respect to the performance of a professional services engagement. For purposes of this definition, partner may include an employee with this authority who has not assumed the risks and benefits of ownership. Firms may use different titles to refer to individuals with this authority.
•  A firm is a form of organization permitted by law or regulation whose characteristics conform to resolutions of the Council of the AICPA and that is engaged in public practice.
• The engagement team is all partners and staff performing the engagement and any individuals engaged by the firm or a network firm who perform audit procedures on the engagement. This excludes an auditor's external specialist engaged by the firm or a network firm. The term engagement team also excludes individuals within the client's internal audit function who provide direct assistance on an audit engagement when the external auditor complies with the requirements of section 610, Using the Work of Internal Auditors.
• Staff are professionals, other than partners, including any specialists that the firm employs.
• A network firm is a firm or other entity that belongs to a network, as defined in ET section 0.400.  A network is an association of entities, as defined in ET section 0.400, Definitions.

Leadership responsibilities are the tone at the top; for example, the engagement partner's communications and actions should emphasize:

• the importance to audit quality of
• performing work that complies with professional standards and applicable legal and regulatory requirements;
• complying with the firm's applicable quality control policies and procedures;
• issuing auditor's reports that are appropriate in the circumstances; and
• the engagement team's ability to raise concerns without fear of reprisals and
• the fact that quality is essential in performing audit engagements. 

https://www.aicpa.org/content/dam/aicpa/research/standards/auditattest/downloadabledocuments/au-c-00220.pdf